In recent times, because of the world wide energy crisis, many proposals for fireplace stoves and heaters have been made. The following prior United States patents reflect some of these proposals which have at least a general relation to the present invention:
U.S. Pat. Nos. 3,880,141, 3,938,496, 3,987,778, 3,995,611, 4,036,205, 4,136,665, 4,141,336.
The present invention seeks to improve on the prior art in a number of respects resulting ultimately in increasing the amount of heat which can be recovered and utilized for living space heating from a given quantity of fuel. In attaining this broad objective, the heating unit according to the invention utilizes several important feature which coact to improve overall efficiency. The most important of these features is a unique maze or manifold chamber for hot combustion products receiving such products from a discharge passage at the top of the fire box and causing the combustion products to flow through tortuous exhaust passages leading ultimately to the flue or chimney after passing through one adjustable and two constantly open non-adjustable exhaust openings leading to the chimney or flue.
A second major feature of the invention is the provision of a heat exchanger passage or jacket surrounding the fire box of the heating unit and formed by an outer shell integrated with the inner fire box shell. Living space air enters the heat exchange passage or jacket space and flows constantly in heat exchange relationship to the hot combustion products simultaneously flowing in the exhaust maze which is isolated at all times from the air heat exchange passage. The heated air enters the living space through a grill covering the outlet end of the heat exchange passage or space.
Another very important novel feature of the invention is the utilization in the combustion products exchaust maze of a very large expanse of metal for heat transfer purposes and having a significant frontal portion of this maze with the fire box therebelow and the doors of the latter projecting into the living space from the fireplace void above the hearth. Direct radiation of large amounts of heat into the living space is thus achieved to supplement hot air flow through the grill. Further significant radiation is achieved through utilization of a three piece thin metal face plate at the front of the fireplace void in thermal contact with the fire box shell and air heat exchanger structure. This face plate also seals the fireplace void against receiving air from the living space around the margins of the heating unit to be lost up the chimney.
The construction of the unit is such that heat radiating from the fire box behind the face plate within the fireplace void cannot directly escape up the chimney but is utilized to further heat and flowing air in the heat exchange passage or jacket. All of these features contribute to maximizing the overall thermal efficiency of the invention in comparison to the known prior art.
Additional features and advantages of the invention will be set forth during the course of the following detailed description.
It should be mentioned that another important objective achieved in the invention is a strong and durable inwardly welded structure which is practical to manufacture and inexpensive compared to many prior art devices.